Automatic toll system

I hate the delays at toll booths. There are automatic systems (EZ-Pass in my area), but they still require special equipment. This idea should eliminate the problem.
Put piezoelectric strips across the road like they are used for traffic sensing at some automatic traffic lights. Cars produce electricity by just driving across the piezo elements. Heavy cars that put more wear on the road also make more electricity. The electric power can be used locally to light traffic signs at night. That has the added advantage that the signs only light up when they are really needed so there is an overall energy saving. Very busy roads could deliver energy to the public grid.
People who are tired of piezo ideas can envision this as loops of water filled hoses with check valves and little turbines. Cars "pump" water through the hoses that runs the turbines. More expensive than piezo elements, but still cheaper than a person in an air conditioned/heated booth holding out a hand for money.